1. Field of the Invention
The present invention relates to polyester-based napped fabrics having a hand resembling that of animal hair and an excellent appearance with high-quality feeling, and having good HARI (anti-drape stiffness) and KOSHI (stiffness), which are usable in a wide variety of end-uses including interior fabrics such as car seat covers and carpets, artificial suedes and clothing. The present invention also relates to tapered fibers constituting the above fabrics and a process for producing such fibers.
2. Description of the Prior Art
Napped fabrics such as standard cut-pile, moquette, double-raschel, velour and velvet have various appearances and hands and have been widely used as interior fabrics such as car seat covers, carpets and flocked fabrics, as well as artificial suedes and clothing.
Napped fabrics with their naps comprising polyester fiber however have stiffer tactility and are significantly poorer in appearance such as luster and brightness, than those with naps made of fibers of acrylic, nylon and rayon, cotton, wool and the like. Besides, when these polyester-based napped fabrics are dyed, they hardly give mild luster like that of napped fabrics made of natural fibers such as wool and silk, and their hand lacks natural feeling, and it is difficult to give them deep color.
For the purpose of improving the appearance and hand of polyester-based napped fabrics there have been proposed various processing techniques, among which the one of tapering naps of napped fabrics made from polyester fiber is important. Various tapering techniques have so far been proposed and most of those that give comparatively good tapered shape of polyester fiber utilize hydrolyzability of polyester.
Japanese Patent Publication No. 40195/1975 discloses a representative process of the above tapering techniques, which utilizes the hydrolyzability of polyester and capillary phenomenon and comprises immersing the ends of polyester fiber naps in an alkali solution and heating the solution to make the naps taper to the ends. For naps having a large length, this process can provide naps being tapered to some extent along their length. For shorter naps such as moquette, velour and velvet, this process however gives poor fabrics being of low strength, too flexible or lacking high quality feeling, since in sufficiently hydrolyzing the ends it hydrolyzes also up to the roots of naps, thereby making fine the whole naps.
Furthermore, when napped fabrics made of conventional polyester fiber are etched to give not sufficiently tapered naps, their dyed products will tend to produce unnatural luster or color, such as "dark fading" or "white appearance" caused by diffused reflection of light. Then, they become inferior to napped fabrics of natural fiber such as wool and silk in the brightness and deepness of color, in mild luster and in natural feeling.
Improvements have also been made in the technique of forming fabrics having tapered naps from polyester fiber.
For example Japanese Patent Application Laid-open No. 133220/1982 discloses a process which comprises tapering by etching a sheath-core composite fiber comprising a cation-dyable polymer. While this process improves to some extent, but not sufficiently, the brightness and deepness of color, it can hardly improve the other drawbacks. Japanese Patent Application Laid-open No. 154435/1982 discloses a process which comprises tapering by etching a sheath-core composite fiber composed of a core polymer containing a delusterant and a sheath polymer having nearly the same hydrolyzing rate as that of the core polymer. No improvements in the development of color and the luster can be expected from this process.
Japanese Patent Application Laid-open No. 65034/1983 discloses a technique which comprises etching a composite fiber having a radiated cross section and containing a delusterant, in a rotating bath containing solely a hydrolyzing agent, thereby providing a tapered fiber by action of centrifugal force. The rates of hydrolysis of the two polymers used in this process are about the same, and the etched fiber does not produce effect of the color development through roughened surface, whereby it gives only light color when dyed.
Japanese Patent Application Laid-open No. 140167/1981 discloses a process for producing artificial fur which comprises treating a napped fabric made of tomenta and pinfeathers of a sheath-core composite fiber having a fineness of 20 to 70 deniers and comprising two polymers having different hydrolyzability, with a hydrolyzing agent containing a thickener, thereby removing the more readily hydrolyzable polymer by hydrolysis. This process however cannot provide a high-quality napped fabric since the naps thus treated give a shining appearance.
Japanese Patent Application Laid-open No. 134272/1981 discloses a technique for splitting the ends of naps which comprises treating naps of a composite fiber comprising two polymers having different hydrolyzability and having a cross section of multilayered or multi-core sheath-core type with a hydrolyzing agent, thereby removing the more readily hydrolyzable polymer. The naps thus treated by this process however are not tapered to the ends and the napped fabric hence shows an unnatural appearance and tactility.
Japanese Patent Application Laid-open Nos. 112306/1980, 112385/1980, 137241/1980 and 201549/1989 disclose a technique which comprises alkali etching napped fabrics with naps made of a fiber containing fine particles, thereby permitting the naps to have roughened surface. The naps thus formed by this technique are however not tapered to the ends, and hence the finished napped fabrics are not improved so much in the hand and tactility, although they show better development of color when dyed. If the naps be ever tapered to the ends by this process, they will be cheap-looking in luster and tactility and liable to be soiled at the toughened surface of the ends, being thus unable to give high-quality feeling.
As stated heretofore, known techniques all fail to provide a high-quality fabric with naps comprising polyester-based synthetic fiber.
Development of a high-quality napped fabric having naps comprising polyester fiber is still strongly desired, since polyester fiber is superior, in durability and resistance to light and yielding of the naps, to other synthetic fibers and natural fibers.